1. Field of the Invention
The present invention relates to earth boring bits and specifically to a welding method for welding a multiplicity of individual sections together to form a rock bit.
2. Description of the Prior Art
A rotary rock bit in general consists of a bit body made by welding separate sections together along seams between the sections. The body of a typical, contemporary bit is constructed of three sections, assembled to engage across 120 degree, machined faces and welded to form an integral body unit. A cone is mounted, on a cantilevered bearing shaft that extends from each section. The assembled bit has a connecting end for connection to a string of drill pipe for rotation about a vertical axis.
In recent years, attention has been focused on improvements to the welding and assembly procedures to improve the integrity of the rock bit. In the prior art method of manufacturing rotary rock bits, a radial weld groove was formed between adjacent sections of the bit. The radial weld groove had sidewalls which converged in an axial direction to form a root region, when viewed. The radial weld groove was filled with a weld deposit by a welding process. Surfaces on adjoining sections were in adjacent relationship but the surfaces were not joined together and the joining of the sections was through the weld deposit. In some cases, the welds were susceptible to failure along the seams, especially due to fatigue cracking. The fatigue cracks typically occurred in the non-fused, weld root region.
A need exists for an improved welding technique which will improve the resistance to failure, especially fatigue cracking, of the seams of rotary rock bits.